For over twenty years, we or one or more of us, have proceeded to develop, construct, and patent a series of annular metal casting units of this type. In addition to the foregoing patents, see also U.S. Pat. Nos. 3,739,837, 4,421,155, and 4,597,432. Each of the units comprised an annular mold having a vertical axis and an annular body circumposed thereabout, which in turn had upper and lower annular ends thereon, relatively inner and outer annular peripheries thereabout, and a bore therethrough, the cavity of which was formed about the axis of the mold and opened into the ends of the mold body, so that the bore of the mold body could form the bore of the table when the unit was supported in the aperture of the table coaxially thereof. The mold body itself comprised a pair of relatively upper and lower casing means which were annular, were circumposed about the axis of the mold, and were superposed on one another so as to have mutually opposing faces thereon which were engaged with one another about the axis to form an annular joint therebetween. The relatively upper casing means in turn comprised an annular case which was relatively thick and substantial axially of the mold, was often monolithic, and had an annular groove in the bottom end thereof. The relatively lower casing means comprised an annular plate which was of course, relatively thin axially of the mold, and was engaged about the bottom end of the case to close the bottom of the groove and form an annular chamber about the axis of the mold. The chamber had an inlet, and it had means such as a series of symmetrically arrayed holes circumposed thereabout adjacent the lower end opening of the cavity, which were connected to the inlet by the chamber and defined an outlet whereby liquid coolant could be charged into the chamber through the inlet, and then discharged through the outlet to direct cool the molten metal body emerging from the cavity at the lower end opening thereof. In the mold, moreover, the case or relatively upper casing member, defined the upper end portion of the mold body at the outer periphery thereof, whereas the plate or relatively lower casing member defined the lower end portion of the mold body at the outer periphery thereof. The case also defined the lower end opening of the cavity at the inner periphery of the mold body, the outlet for the coolant discharge adjacent the lower end opening of the cavity, and the connection between the inlet and the outlet provided by the chamber. In some versions, such as in that shown in U.S. Pat. No. 4,597,432, the metal casting unit was operatively inserted in the aperture of the table from a point therebelow, and therefore, the plate was projected relatively radially outwardly of the axis of the mold from the joint between it and the case, so as to form a flange on the lower end of the mold, at opposite sides thereof, which was operable to engage the bottom of the table so that it could be secured to the table to provide support for the metal casting unit when the unit was inserted in the aperture of the table. In other versions, such as in those shown in U.S. Pat. Nos. 5,040,595 and 5,119,883, the metal casting unit was operatively inserted in the aperture of the table from above the table, and therefore, the flange was formed on the upper end of the case to engage the top of the table and provide support for the unit as it hung in the aperture therebelow.